We report the molecular recognition for nucleoside triphosphates inside the ligand-modified water-soluble organic-inorganic hybrid gels composed of polyhedral oligomeric silsesquioxane (POSS). The series of ligands were designed to make hydrogen bonds with each nucleobase and introduced into the hybrid gels. From the titration experiments, the binding constants between the ligand inside the gels and nucleosides were evaluated. Accordingly, it was found that the ligands inside the gels can form a stable complex only with the target nucleoside triphosphate which has the complementary pattern of the hydrogen bonds (K-a = G-gel/cytidine triphosphate (CTP), 3.5 x 10(8) M-1; U-gel/adenosine triphosphate (ATP), 1.6 x 10(3) M-1; A-gel/uridine triphosphate (UTP), 1.9 x 10(7), respectively). With other nucleoside derivatives which have different numbers of phosphate units or different types of nucleobases, the much weaker interaction was detected. These data indicate that the complex formation only with nucleoside triphosphates should occur inside the hybrid gels, and selective recognition of each nucleoside triphosphate can be accomplished. (C) 2015 Elsevier Ltd. All rights reserved.